How to tweak ZFS parameters? | zfs_arc_min

[The_Saver]

Hello everyone,

How can I tweak ZFS parameters?

I cannot follow guides because the paths to ZFS as well as modprobe do not exist.

I would like to set my ZFS cache size up from the default of 0.4% of total RAM (which is the standard settings as far as I can tell) to 2 GB RAM or so.
I found out that the setting is called: zfs_arc_min

I tried to make a small script to do the job:

The script was based off of this thread:

ZFS tune (zfs_arc_min, zfs_arc_max) ?

Migrate from CORE to SCALE. Previous (CORE) i can control ZFS over sysctl (use tunables). How i can control zfs_arc_min, zfs_arc_max on SCALE on boot ? I try use script/command as: modprobe zfs zfs_arc_min=53687091, zfs_arc_max=1073741824 and modprobe zfs c_min=53687091,c_max=1073741824 but...

www.truenas.com

When I try to run the command he ran "cat /proc/spl/kstat/zfs/arcstats | grep c_" I get the following error:

As well as modprobe:

Bonus info: I have created the following thread, but I deemed this to be worth its own separate thread. Basically why I want more ZFS cache is because it seems like the minimum for me is just below 1 GB and it makes my Rsync transfers pause all the time which makes my transfers take 4 times as long https://www.truenas.com/community/t...emory-for-services-rsync-is-very-slow.102747/

 

[winnielinnie]

and it makes my Rsync transfers pause all the time which makes my transfers take 4 times as long

You're going off in the wrong tangent then. Rsync is metadata-heavy.

Please see this thread instead:

ZFS "ARC" doesn't seem that smart...

Without yet resorting to adding an L2ARC, is there a "tuneable" that I can test which instructs the ARC to prioritize metadata? I upgraded from 16GB to 32GB ECC RAM. Yet there is zero change in this behavior. This keeps happening: I run regular rsync tasks from a few local clients, which is...

www.truenas.com

And more specifically this post:

ZFS "ARC" doesn't seem that smart...

Without yet resorting to adding an L2ARC, is there a "tuneable" that I can test which instructs the ARC to prioritize metadata? I upgraded from 16GB to 32GB ECC RAM. Yet there is zero change in this behavior. This keeps happening: I run regular rsync tasks from a few local clients, which is...

www.truenas.com

Unless you mean when Rsync is actually transferring a large file it hangs?

EDIT: Keep in mind that the syntax between Core -> SCALE is different, and thus I'm not sure how to enter the variable name for a SCALE (Debian-based) system. It might be a GUI issue, or we're missing something else:

ZFS "ARC" doesn't seem that smart...

I find that the number did surpass 4GiB, but nowhere close to 8GiB. I wonder if it reports a different value with... arc_summary | grep "Metadata cache size (current)" ...during your tests? If I strictly use full rsync crawls (directory tree crawls for the entire datasets) for three...

www.truenas.com

 

[The_Saver]

You're going off in the wrong tangent then. Rsync is metadata-heavy.

Please see this thread instead:

ZFS "ARC" doesn't seem that smart...

Without yet resorting to adding an L2ARC, is there a "tuneable" that I can test which instructs the ARC to prioritize metadata? I upgraded from 16GB to 32GB ECC RAM. Yet there is zero change in this behavior. This keeps happening: I run regular rsync tasks from a few local clients, which is...

www.truenas.com

And more specifically this post:

ZFS "ARC" doesn't seem that smart...

Without yet resorting to adding an L2ARC, is there a "tuneable" that I can test which instructs the ARC to prioritize metadata? I upgraded from 16GB to 32GB ECC RAM. Yet there is zero change in this behavior. This keeps happening: I run regular rsync tasks from a few local clients, which is...

www.truenas.com

Unless you mean when Rsync is actually transferring a large file it hangs?

EDIT: Keep in mind that the syntax between Core -> SCALE is different, and thus I'm not sure how to enter the variable name for a SCALE (Debian-based) system. It might be a GUI issue, or we're missing something else:

ZFS "ARC" doesn't seem that smart...

I find that the number did surpass 4GiB, but nowhere close to 8GiB. I wonder if it reports a different value with... arc_summary | grep "Metadata cache size (current)" ...during your tests? If I strictly use full rsync crawls (directory tree crawls for the entire datasets) for three...

www.truenas.com

Thank you.

Adding this configuration step seems to have fixed my issue!

System --> Tunables

It equals to about 2.9 GiB RAM, which is a perfect minimum ZFS cache value for 32 GiB RAM with my use case.

 

[winnielinnie]

There's something funky going on, though. It still does not explain why ZFS is being tentative with the ARC, yet "Services" (still unsure what that means, to this day) consumes the overwhelming majority of your RAM.

Again, I don't have a legit SCALE system to play around with (sticking with Core), so I'm not sure if it's unique to SCALE users and/or a bug in the way the GUI "reports" memory consumption?

 

[Patrick M. Hausen]

I would start searching for the memory hogs with top/htop ...